Refrigeration



Jul 13,1937.

c. ca. MUNTERS REFRIGFRATION 15 Sheets-Sheet 1 Filed March 50,- 1954 lNV TOR July 13, 1937. c. G. MUNTERS 2,086,532

REFRI GFRATION Filed March so, 1934 15 Sheehs-Sheer. 2

I INVENTOR 5 figw RNEY July 13, 1937 c. G, MUNTERS REFRIGFRATION Filed March so, 1934 15 Sheets-Sheet '5 jNvgNToR BY A ATTORNEY July 13, 1937. c. G. MUNTERS 2,086,632

REFRIGFRA'JION Filed Marbh so, 1934 15 Sheets-Sheet 5 I ls/Ya'ylNvENTOR ATITORNEY July 13, 1937. c. G. MUNTERS REFRIGFRATION Filed March 30, 1934 15 Sheets-Sheet 6 z /9 INVENTOR ATTORNEY July 13 1937. c. G. MUNTERS REFRIGFRATION .Filed March so, 1934 15 Sheets-Sheet 8 END OF THE HEAT/N6 PEP/0D ml IlI|I I I I I I I I I I I I I I I I I I I I I II I Ill I I I INVENTOR A; ATTORNEY July 13, 1937. c. G. MUNTERS REFRIGFRATION l5 Sheets-Sheet 9 Filed March 39, 1934 Assam-W0 PER/00 lHHlllllllllllllll a llllllllllllllIHIIIHIIIHIHIIIIIIIlll INVENTOR /%z BY W41 4, ATTORNEY July 13, 1937. c. G. M'UNTERS 2,086,632

REFRIGFRATION Filed March so, 1934 15 Sheets-Sheet 1o 6% INVENTOR 0 L9 BY ATTQ RN EY July 13, 1937. I c. G. MUNTERS 2,036,632

REFRIGFRATION I Filed March 30, 1954 15 Sheets-Sheet 11 F/iy 0. Ml7 INVE'NTCR A ATTORNEY July 13, 1937- c. G. MUNTES REFRIGFRATION Filed March 30, 1954 15 Sheets-Sheet 13 INZENTOR flax/$446.4 A; ATTORNEY July 13, 1937. Y c. G.IMUNTERS REFRIGFRATION Filed March 50, 1934 15 Sheets-Sheet l4 INVENTOR KT I'ORNEY Patented July 13, 1937 UNITED STATES PATENT OFFICE REFRIGERATION Application March 30,

1934, Serial No. 718,136-

In Germany December'16, 1933 81 Claims. My invention relates to refrigerating systems of the kind having periods of evaporation at low pressure alternating with periods of expulsion of refrigerant and condensation at higher pressure, and in which a small part of the absorption liquid is heated at a time during the expulsion periods while the greater part ofthe absorption liquid is maintained in cold condition.

Among the objects of my invention are:

To provide means in a system of the type above set forth for quckly raising and lowering liquid to control admission of refrigerant vapor to absorption liquid;

To provide reliable means for governing the liquid column for forcing vapor into the absorption liquid;

To provide an apparatus of the kind referred to which will readily start by mere application of heat, through liquid maybe displaced out of the parts in which it is disposed in normal operation;

To provide a minimum temperature variation of the bulk of absorption liquid and avoid heat losses from absorption liquid;

To provide regulation of liquid column height for driving refrigerant vapor into absorption liquid without drawing a considerable amount of liquid out of the circulating portion of the liquid circuit;

To provide constant liquid heads on vapor-lift members actively operating during the expulsion periods;

To provide an improved analyzing effect in a system of the kind set forth;

' forming a part of this specification, of which:

Fig. 1 is a showing, partly in cross-section, of an absorption refrigerating system embodying certain phases of the invention;

Fig. 2 is a back view of the upper part of an actual apparatus built in accordance with the present invention;

Fig. 3 is a back view of the lower part of the apparatus of Fig. 2, Figs. 2 and 3 constituting a single elevational view when joined on the line Fig. 4 is a side view of the structure shown in Fig. 2;

Fig. 5 is a side view of the structure shown in Fig. 3; Figs. 4 and 5 constituting a complete side view of the apparatus when joined on the lines Fig. 5a is a view from the opposite side of the structure shown in Fig. 3;

Fig. 6 is a diagrammatic showing of the apparatus of Figs. 2 to 5 illustrating the action during the heating period.

Fig. 7 is a similar view showing the action at the end of the heating period;

Fig. 8 is a similar view illustrating the action during the absorption period;

Fig. 9 shows another embodiment of features of the invention;

Fig. 10 shows a modified form of cycle regulation;

Fig. 11 shows an evaporator structure and regulation;

Figs. 12 to 15 disclose still another system embodying the invention; and

Fig. 16 shows a modification of a counter-lift employed in the system.

In each of the systems disclosed, the parts are made of suitable metal and the systems are hermetically sealed. For illustrative purposes it will be assumed that the systems are charged with an ammonia-water solution of, for example, 30% concentration. With these fiuids the parts may be made of steel pipes and vessels welded together. Other refrigerants may however be used as will be obvious to those skilled in the art after a study of the invention.

The system shown in Fig. 1 includes an absorption liquid reservoir ID of sufficient volume to hold the bulk of absorption liquid in the system. This reservoir is preferably exposed to the cooling influence of surrounding air. To one side of reservoir I0 is a vessel H which may be termed a generator or separator or be considered as a part of the vapor expeller. This vessel is not directly heated, though it may be. In the embodiment illustrated, the contents of vessel ii are heated by a conduit l2 including a vapor lift coil I3 which is in heat exchange relation with a source of heat such as an electric heater. An electric heater 8 is disposed in a flue or pipe M. Instead of an electric heater the heated zone may be heated by a gas flame or other source 0! heat. Conduit I 2 is connected at the bottom. to the bottom of vessel or tube H and at the top to the top of vessel H.

A conduit 15 is connected to the bottom of vessomewhat above overflow edge 21.

sel l I and to the bottom of reservoir l0 for flow of weak' absorption liquid from the generator or expeller to the storage reservoir l5.

Connected to the top of reservoir i0 is a vertical conduit 16, the upper end of which is .connected to a vessel I! which I will term an excess vapor vessel and which is normally filled or substantially filled with liquid. A conduit I8 is connected to the lowerpart of reservoir lo and extends upwardly to connect with vessel ll. This conduit l8 has a horizontal loop constituting an absorption liquid cooling element 5 having heat transfer fins l9 continuously exposed to the cooling effect of atmospheric air. Also connected to vessel I1 is a strong liquor conduit 28.

' Parts l6, l'l, l8 and 20 constitute an absorption liquid containing structure extending above reservoir ID. This structure is connected to the liquid space of the absorption liquid containing part of the system so that, practically at all times, this structure is filled or substantially filled with liquid due to the fact that, these parts being exposed to atmosphere, the temperature of the fluid therein is such that for the pressures prevailing in the system and in view of the concentration of solution, all the gascan be dissolved and remain in solution form.

The bottom of pipe 20 is connected to a conduit 2i surrounding pipe l5 and forming therewith a liquid, heat exchanger 22. A conduit 23 extends between the other end of conduit 2| and the lower part of anannular chamber 25 formed between an outer cylinder or member .25 and an inner cylinder 26. Chamber 2% is closed at the bottom except for conduit connections, and is open at the top. vThe upper edge of cylinder 26 provides a waterfall or overflow edge 21. The space 28. within cylinder 251s connected at the bottom with a tube 2%. Tube 29 and space 28 form a holder for a down-leg or head column for a gas lift circulator and a counter-lift.

A conduit 30 is connected to the bottom ofcolumn tube 29 and is wound around tube id to form a vapor-lift or gas lift member inheat exchange relation with -the source of heat and thence extends upwardly to connect with the gas separation chamber or generator vessel ll. Both conduits l2 and 30 are connected to vessel ll Vapor-lift member 8| is the prime mover for circulation of liquid between the-storage reservoir it and the generator or source of heat during the heating or expulsion periods.

A conduit 32 including a gas lift or vapor-lift member 35 wound around flue Hi to receive heat therefrom is connected between the bottom of column tube 29 and the bottom of chamber 25. The upper part of conduit '32 inclines downwardly toward chamber 24 to form a resistance trap.

Each of the gas lift members is so narrow that a gas bubble substantially fills out the'cross sectiono! the tube. V

A volume variation vessel 35 is connected by means of conduits 36 and 31 .with the upper of member 25 and the lower part of tube: 29..

A conduit 38 extends upwardly from conduit 36- within a rectifier chamber 35=and contains bai' fies 45.. A condenser coil ti is connected to chamber 39 and is imbedded in the same fins l9 as absorber element 9. Connect d to rectifier jacket 38 at slow level is a conduit 52 which extends upw'ardly'and opens at the top within a dome 43 of an evaporator 45. Connected to the evaporator 45 is. .a draining meansincluding a loop 45." A second loop-Q1 has an opening withabout on a level with the lower part of the dome 43 is a conduit 49 which constitutes an overflow conduit and which extends downwardly into heat exchange relation with the volume variation vessel 35 and which is connected with conduit It justbelow a level R. A conduit 50 is connected with conduit l8 at the level R by means of a small aperture 5| and is connected at its upper part to conduit 36.. A charging and purging valve 52 is provided in the top of vessel H and vessel 35 may be provided with a valve for trimming the charge in the apparatus. A thermostat bulb 53 is arranged in heat exchange relation with conduit is above the level R.- This bulb is connected by means of a tube 54 with a bellows or other movable member 55 which is adapted by expansion and contraction to tilt a lever 55 on which is mounted a mercury contact switch 5i operative to open-or shut electric connections for supplying current to the heater 8; Also acting on member 55 is a second thermostat including a bulb 58, a tube 59, and a bellows 60. Bulb 56 is subject to the temperature of the atmospheric air which surrounds the liquid containing parts of the system including the reservoir l0 and parts l6, l1 and I8 which are not insulated. The purpose of bulb 581s to take care of variations in-temperature of the atmosphere to adJ'ust the action of bulb 53 to the efiects of atmospheric or surrounding temperature on the system.

The members 22, 35, 29, '25, H, and the liquid lift conduits and the immediately associated parts, should be imbedded in insulation M as shown. The amount of liquid contained in the system should be enough to fill the parts l0, i6, i1, I8, 20, and all other parts below the top of reservoir Ill and to such higher level as will fill vessel 35 less the amount 01. liquid contained in the parts of conduits l5, l8 and Eli and vessel i? above the top of vessel 85. It is intended that the apparatus will be so constructed that if all the liquid should seek its lowest level it would not rise up to such a level that on subsequent heating absorption liquid would be driven into the evaporator. This level should be preferably slightly below the top of vessel 35. The vessel 85 should be 01' sufiicient capacity to hold as much absorption liquid as 1s contained in the system in normal operation at the end of the heating period above the point of connection of pipe 23 with are in open gas and liquid communication and therefore anyliquid in chamber 26 will flow downwardly or try to flow downwardly through conduit 32, displacing, liquid into the volume variation vessel. Likewise the two higher levels prevailing during the previous heating period at Y and Z in pipe 50 and vessel I I respectively, will seek the common level and will drop. The liquid in vessel .II will flow downwardly therein and through conduit l5to reservoir II. There being 75 wiseliquid will be displaced from the pipes connected with reservoir l0 through pipe 20 and through the same path as just described to the volume variation vessel. When the level in pipe 50 has fallen down to the level R gas can enter through the hole 5|. The hole 5| is now in direct gas receiving communication with the evaporator 45 through the conduits 50, 36, 38 and42.

Gas entering pipe l8 through aperture 5| will flow upwardly therein causing circulation of absorption liquid through pipes l8 and 20 and vessels l0 and il. Since there is liquid in the pipe 18 all the way up to the vessel H, the pressure is less and less going up in the liquid column and the gas will naturally go upwardly within this pipe to the lesser pressure space. The gas fiowing upwardly in conduit 18 is absorbed in the weak liquid therein and, unless too much gas is admitted, the rejection 01' heat through absorber fins l9 will besufilcient so that the gas may be entirely absorbed and due to the arrangement and temperature of the vessel i1 and p pes l8, l6 and 20'they will continue to hold liquid above the level R.

In order to sustain inflow of gas through aperture 5| into pipe l8 it is necessary that there be a higher pressure on the gas than the pressure 'at the opening 5| within pipe l8. This higher pressure is obtained without the use of a liquid trap between the generator and the evaporator as follows: The liquid has now fallen in chamber 24 to a level below the level R and we may consider that it has fallen to the level V, namely the point of connection of conduit 23 with chamber as and the high point in conduit 32. The pipe 23 contains liquid, which liquid is unbroken through conduit 2| and pipe 20 and through the vessel l1 and through pipes l6 and it to' the aperture 5|. This unbroken liquid communication also extends through pipe l5 to the contents of the separator vessel ll. Consequently we may consider that we have a U-tube containing liquid in which the left-hand branch of the U-tube has a level up to R and the righthand branch has a level up to V. The liquid above the level R'need not be ccnsidered because that equalizes in pressure through itself. Consequently the difference in height which is represented by H between the level R and the level V represents the height of liquid column preponderance on the left-hand side and consequently the pressure on the gas just above the liquid in chamber 24 is higher than the pressure at the level R within pipe I8 by the amount of the head H. Pressure is transm tted equally through gas and therefore this pressure may be said to act upwardly within chamber 24 and on to the gas which is in pipe 50 to force it into the conduit l8. Another way of looking at it is that the temperature of the parts ll, 20, I6 and i8, in view of the concentration of solution therein, causes the liquid to be he'd up in' these parts, so to speak, by suction, wherefore, with respect to the level V, there'is a suction or reduced pressure at the higher level R due to this level being at a higher point in the liquid system and due to the fact that the only difierences in pressure are those occasioned by diiferent heights of liquid. It mightbe thought that the gas in aperture 5| would expand and allow liquid to fall down in pipe l8 but there is a local circuit including pipes i 8 and I6 and vessels i0 and I1 so that when gas is introduced into pipe iii the heavier solid column of liquid in pipe IB tends to push downwardly into the vessel i0 and upwardly through the bottom part of pipe l8. This might be explained by stating that the bubble entering through the aperture 5! is like a cork introduced below the surface of a body of liquid. The level in vessel II will likewise be generator and from the evaporator to the ab-,

The

sorption liquid circuit through pipe 50. withdrawal of gas from the chamber 35 and vessel i 1 serves the purpose of reducing the pressure and eifecting cooling of the liquid contained within the parts imbedded in insulation.

It is'necessary that the vapor pressure of the solution imbedded in insulation be brought down in order that evaporation will take place in the evaporator, suificient to produce refrigeration. Thus I provide a means for rapidly bringing down this pressure without the utilization of an external cooling medium applied to the liquid within the insulation or what may be termed the liquid within the hot part of the system during the heating period. Another factor of importance is that the withdrawal of gas from above the surface of liquid in,the chamber 24 and in vessel II will result, at the beginning of the absorption period, and continung throughout a substantial portion thereof, in continued ebullition of liquid in the pipes within the insulation, thus still further facilitating the withdrawal of gas from all the liquid contained within the insulation. The residual heat in the insulation and in the metal parts imbedded in the insulation together with the reduction in pressure in the gas space will cause continued ebullition in the gas lift members 13, 3| and 33 and other liquid containing parts after the heat has been shut off,

thus bringing all the warm liquid quickly into the conduit l6 through the reservoir l0 and back into the conduit i8. Thus the liquid in the reservoir I0 is gradually enriched. There will not be violent movement of liquid within the reservoir in but we may consider that the separation between the rich liquid and the weak liquid gradually descends in the reservoir I0 until all the liquid therein becomes enriched. During the absorption period, the absorbed refrigerant increases the volume oi absorption liquid corre- Inasmuch as the sponding to the amount of refrigerant absorbed. This increase of absorption liquid is taken care i of by overflowirom the absorber circuit l6, i6,

ll, it, through conduits 2G, 2! and 23, and through conduit 32 and conduitfil into the volume variation vessel 35. At the end of the absorption period, the vessel 35 should be substantially filled with absorption liquid to about the level K. In this overflow, the level in vessel 35 will stand approximately the same as the level in conduit 32 and therefore there is an overflow or waterfall between the top bend of conduit 32 and the level therein corresponding to the level in vessel 35. By means of this waterfall the variation of liquid level in vessel 35 is isolated from the absorption liquid circuit.

An apparatus of this kind has a very rapid drop in pressure at the beginning of the absorption period, and since the body to be cooled which is in heat exchange relation with evaporator 45 is warm at this time, there will be an intense evaporation of liquid refrigerant and more gas may pass through aperture 5! than can be taken care of by the cooling provided by absorber 9. It is therefore desirable to govern or regulate the rate of absorption and consequently rate of gas supplied to the absorption liquid circuit. If some means were not provided to slow down this absorption liquid circulation, so much gas might enter the liquid containing structure above reservoir in that the liquid would be pressed down to break the circulation circuit through conduits l8 and i6 (assuming for the moment that the conduit 20 were not connected at its upper end to vessel ll) and a break in the local absorption circuit would prevent further absorption until such time as the refrigerant gas became absorbed, which could not very well take place when the circulation has stopped. Should the liquid surfaces in pipes l6, l8 and 20 fall below aperture 5|, the circulation of absorption liquid through these pipes cannot restart without initiating a new expulsion period to raise the liquid in chaming the level in chamber 24 in view of the overflow. However, a variation of liquid column affecting the absorption liquid circulationcan be obtained in the U-tube represented by conduits 2B, 2!, and 23 by varying the left-hand branch. The possibility of doing this means that it is not necessary to use a large volume of liquid to produce a variation in driving head as would-be the case if it were necessary to raise the liquid in vessel 35 to accomplish this.

' Assume now that more gas enters conduit i8 thancan be absorbed due to heat dissipation that there can still be liquid communication between pipes l6 and I8 so that the liquid circulation through pipes l8 and I6 can continue. How- I ever, when the gas enters the pipe 20, the column of liquid in pipe 20 is reduced, and. since the liquid overflow height in pipe 32 is constant, there will be a lesser head acting on the gas in chamber 24 due to the liquid column in pipe 20 above the 'overflow edge in pipe 32 being lessened. The

same gas accumulated in the upper partof vessel i'l will tend to depress liquid downwardly in the pipes it and IE but liquid depressed in these pipes displaces liquid through pipe l5 and into the vessel H and since there is no overflow for the liquid from this vessel during the absorption period'the level or surface therein will rise as' the level lowers'in conduit 20. This rise of liquid in vessel ll decreases the liquid column in pipes l6 and i8 acting upon the gas in vessel ll corresponds to the volume of liquid which is raised within generator vessel H above the level V. The vessel H is of less hbrizontal cross stoiion than the vessel I1 and consequently a small height within vessel" ll below the point of connection of conduit 20 therewith represents a higher variation in level in l i H. The maximum height towhich-the level can be raised in the vessel ii and lowened'in conduit 20 relative to the level in vessel i7; is the height H because at this point the rise 0? liquid in vessel ii and lowering of liquid in conduit 29 has equalized the column difference between the levels R. and V which was produced to cause circulation.

Assume that the liquid in vessel I? has been depressed so that it stands at A1 and the surface of liquid in pipe 20 stands at the level As. The difference between these levels is represented by the height A: and this same height A: will be the amount that the liquid is raised in. the vessel ll.

Thepressure difference on the two sides oi the aperture H has now been reduced vby an amount equivalent tothe height A3. 'dnother way as putting it is that the liquid column acting on the gas in conduit on has been reduced due to the liquid level in conduit 20 by an amount equal "rise of liquid level in vessel 9! and the lowering oi to the column A3. Thus the effective driving force.

for the absorption liquid circulation is now equal to the difl'erence between the column 1-! and the column .As. The reduced pressure difierence:-

causes less gas to flow through aperture 5| without stopping the circulation of liquid through conduits l8 and i6 and thus time is provided for the gas to be absorbed so that the liquid rises again in vessel ll. Of course, if the reduction in driving head should increase to the maximum holding absorption liquid thereon. Thus the driving head for forcing gas into the absorption liquid circuit is automatically regulated to suit the absorption capacity and this is accomplished by a means separate from the local absorption circuit 7 through aperture 5i and the liquid rises in conso that this circuit can function to obtain the best absorption effectl Furthermore the regulation is accomplished with a very small quantity of liquid and without causing a variation of liquid head in the volume variation vessel or other wide member of the system. Regulation takes place in the same manner if vapor forms in vessel l1 due to lowering of pressure.

I prefer to connect the pipe 20 with vessel l'l some distance below the top thereof so that the upper part of vessel I! can constitute a dead space for accumulation of any extraneous gases which may find their way into the apparatus in the filling process or which may be develped therein during the operation of the apparatus. Suchextraneous gases may be purged out by means of the valve 52. The foreign gases collected in the upper part of vessel I! have no efl'ect on the absorption so long as these gases form not more than a volume filling vessel i! above the point of connection of conduit 20 thereto at the lowest pressure prevailing in the apparatus. Thus an adequate space can be here provided for taking care of foreign gases without having them adversely affect the operation ofthe apparatus. The apparatus preferably contains corrosion preventing materials such as sodium chromate.

The absorption period continues until the gas is substantially entirely evaporated from the evaporator i5 and this vessel is substantially empty.

absorption liquid circulation circuit, through conduit 50, be closed.' This I accomplish by means of the vapor-lift or gas lift or counter-lift member 33 and the conduit 32. During the absorption period, some liquid flows through the conduit 32 from the chamber 23 downwardly to the bottom of column 29. During the heating period, vapor is expelled from solution in the coil 33 due to the heat and since there'is a high column of unbroken liquid in the tube 29, the vapor formed tends to rise in tube 32. There is thus a lifting action imposed on liquid in tube 32 and liquid is conveyed upwardly to chamber 23. This liquid cannot flow through conduit 23 (at least as soon as liquid is raised to level Z in vessel II, which is accomplished primarily by vapor-lift 3i) since this conduit 23 has no place" permitting expansion or receipt of liquid and therefore the liquid, so to speak, piles up in the chamber 23 and rises up to the overflow edge 21. It can rise no higher than the overflow edge 21 because on reaching this height it overflows into the tube 23. Thus there is set up a local circulationfrom tube 29 through conduit 32 and vapor-lift coil 33 and upwardly inchamber 23 over the overflow edge and back down into the column or tube 23. The rise of liquid in chamber 24 (and vessel ll) exerts a pressure influence in the liquid part of the system communicating therewith. This pressure influence communicates through the conduit 23, conduit 2i, conduit 23 and vessel I1 into conduit l8 and raises the pressure in conduit II at aperture 5i relative to pressure in conduit 33 so that liquid is forced out from conduit I! edge 21.

duit 50 to the height Y which is at substantially the same level as the overflow edge 21. Looking at it another way, there is gas communication between the surface of liquid in chamber 23 and vessel Ii and the surface of liquid in conduit 50 and therefore these three liquids, being in unbroken liquid communication, will seek the same level. Thus the conduit 50 is closed up by liquid so that gas is prevented from entering the absorption liquid circuit.

Simultaneously the coil 3| is heated. The production of vapor in this coil causes flow of liquid upwardly therein and through conduit 30 into the member II where vapor is separated from liquid. The liquid flows downwardly in member II and thence through conduit l5 and into the storage vessel or reservoir I0; Liquid further circulates throughconduit l6, vessel I1, conduit 20, conduit 2i, conduit 23, and upwardly through chamber 24 and into the column 29. In order for the liquid 'to flow by gravity through the conduits, the level will be higher in chamber II than the overflow Thus the coil 3i produces circulation between the reservoir l0 and the generator. Simultaneously the coil 13 is heated and vapor expelled therein, which vapor causes circulation from the lower part of member ll through conduit i2 and to the upper part of member I I. This is a local circulation, for expelling refrigerant from solution. Coil i3 is provided so that vessel ll need not be heated and can be as narrow as possible to hold a minimum of liquid. If vessel I i were narrow and heated, liquid would be boiled upwardly carrying liquid into the vapor line. The absorption liquid is heated a little at a time, under substantially continuous circulation, the refrigerant vapor being expelled, and the residual weak liquid passes back to the reservoir l0 while preheating the rich liquid passing through conduits 20, 2|, and 23 to the generator and itself being cooled and stored in the reservoir. It will be seen that the heat exchanger is separated from the overflow edge 21. This provides an analyzing of the vapors expelled in the generator which serves to remove entrained water vapor. Vapor expelled from the absorption liquid passing up-. wardly in conduit 32 passes upwardly in member 23. The vapor from all the vapor-lift coils passes from the top part of member 23 into conduit 36 and through conduit 33 to the condenser I. As the refrigerant vapor is driven oi! the level lowers in vessel 33.

In the condenser ii, the refrigerant vapor is condensed and it flows downwardly into the rectifying pocket 33. The condensed liquid ammonia acts to cool the vapor passing through conduit 33 to further condense out entrained water vapor. Due to the fact that the member 33 contains liquid refrigerant at the same pressure as within the pipe 33, pure ammonia cannot be condensed in this rectifier. The liquid refrig- 

